Method for Checking a Collision Between Two Driverless Transport Vehicles, Driverless Transport Vehicle, and System Having a Plurality of Driverless Transport Vehicles

ABSTRACT

The invention relates to a method for checking a collision between a driverless transport vehicle (1) and a further driverless transport vehicle during planning of a movement of at least the driverless transport vehicle (1). The invention further relates to a driverless transport vehicle (1) and to a system having a plurality of driverless transport vehicles.

BACKGROUND

The invention relates to a method for checking a collision between twodriverless transport vehicles, a driverless transport vehicle and asystem having a plurality of driverless transport vehicles.

For an automatic movement of driverless transport vehicles (alsoreferred to as: automated guided vehicle), a planning of a path can becarried out within a graph. The graph is assigned to the environmentwithin which the driverless transport vehicle should move automatically.The determined or planned path is assigned to the route which thedriverless transport vehicle is intended to travel.

EP 2 818 954 A2 discloses a method for planning a virtual track orvirtual guide line along which a driverless transport vehicle shouldmove automatically within an environment from a starting point to adestination point. The environment comprises intermediate points androute sections connecting the intermediate points, the starting pointand the destination point. A graph is assigned to the surroundings, thenodes of which are assigned to the points and the edges of which areassigned to the route sections of the environment.

If a plurality of driverless transport vehicles are located in theenvironment, the planning of the path should also comprise an avoidanceof a collision of two driverless transport vehicles.

SUMMARY

It is the object of the invention to provide an improved checking of acollision of the driverless transport vehicles with a further driverlesstransport vehicle within the framework of a planning of a movement of adriverless transport vehicle.

The object of the invention is solved by a method for checking acollision between a driverless transport vehicle and a furtherdriverless transport vehicle during a planning of a movement of at leastthe driverless transport vehicle comprising the following process steps:

-   -   providing two-dimensional models of the driverless transport        vehicles,    -   determining an area covered by the driverless transport vehicle        which the driverless transport vehicle covers during the planned        movement and    -   determining a further area covered by the further driverless        transport vehicle, which is covered by the further driverless        transport vehicle during the planned movement and checking a        collision between the driverless transport vehicle and the        further driverless transport vehicle by checking the two areas        covered for any overlap or checking a collision between the        driverless transport vehicle and the further driverless        transport vehicle by checking the area covered assigned to the        driverless transport vehicle for any overlap with the        two-dimensional model of the further transport vehicle.

The method according to the invention is preferably executed by anexternal computer, in particular a so-called fleet manager. A furtheraspect of the invention therefore relates to a system comprising thedriverless transport vehicle, the further driverless transport vehicleand a computer which is able to communicate with the driverlesstransport vehicles, wherein the computer is adapted to carry out themethod according to the invention.

The driverless transport vehicle is, for example, a mobile robot. Thedriverless transport vehicle designed as a mobile robot can comprise arobot arm with a plurality of successively arranged members which areconnected by means of articulations. The robot arm can, for example, befastened to the vehicle base body. The electronic control device formoving the wheels can also be adapted to move the robot arm.

The driverless transport vehicle can preferably be configured as aholonomic or omnidirectional driverless transport vehicle. In this case,the driverless transport vehicle comprises omnidirectional wheels,preferably so-called Mecanum wheels which are activated by theelectronic control device.

According to the method according to the invention, accordingly forchecking the collision (collision checking) during planning, themovement of at least one driverless transport vehicle is taken intoaccount. This movement is modelled according to the invention as thearea covered which the driverless transport vehicle should coveraccording to the planning of its movement. Should the further driverlesstransport vehicle be stationary according to the planning, it is checkedwhether this area covered overlaps the two-dimensional model of thefurther driverless transport vehicle. If this is not the case, acollision-free movement of the driverless transport vehicle is thenobtained. If on the other hand the two-dimensional model of the furtherdriverless transport vehicle overlaps with the area covered, inparticular the planning or the part of the planning in question is thendiscarded.

If the further driverless transport vehicle also moves according to theplanning, the movements of both driverless transport vehicles are thustaken into account in the collision check, by checking whether the twoareas covered overlap. If this is not the case, collision-free movementsof both driverless transport vehicles are then obtained. If on the otherhand the two areas covered overlap, in particular the planning or thepart of the planning in question is then discarded.

The driverless transport vehicle should in particular move within anenvironment. The environment is in particular assigned a graph which hasa plurality of nodes and edges connecting the nodes. The edges areassigned route sections of the environment and the nodes are assignedthe two ends of the points of the environment assigned to the routesections. For the planning of the movement of the driverless transportvehicle, in particular a path is determined within the graph, whichcomprises a plurality of edges of the graph. This results in a routewhich comprises route sections assigned to the edges of the graph. Thedriverless transport vehicle can then automatically follow the route.

The collision checking according to the invention is then preferablypart of the planning of the path, wherein those edges for which acollision is identified are discarded.

It can be provided that the driverless transport vehicles are eachloaded with at least one useful load. Preferably the two-dimensionalmodels are therefore two-dimensional models of the driverless transportvehicles loaded with the useful loads, preferably two-dimensional convexmodels of the driverless transport vehicles loaded with the usefulloads. A subset of a Euclidean space is convex if for every twoarbitrary points pertaining to the set, their connecting section alwayslies completely within the set. The two-dimensional convex modelstherefore comprise no indentations. The use of two-dimensional convexmodels has the advantage that it can be checked relatively efficientlyautomatically whether they overlap. In particular, the so-calledseparation theorem can be used here. It can thus be prevented thatprotruding parts of driverless transport vehicles or their useful loadmove into the indentations of other driverless transport vehiclesvehicles when the identified plans are executed. Such maneuvers are inparticular undesirable in cases of cumbersome and heavy useful loads.

One aspect of the present invention accordingly relates to the use of atwo-dimensional convex model of a driverless transport vehicle loadedwith a useful load for checking a collision with a further driverlesstransport vehicle or a method for checking a collision between adriverless transport vehicle and a further driverless transport vehiclefor a planning of a movement of at least the driverless transportvehicle, comprising: providing a two-dimensional convex model of thedriverless transport vehicle loaded with a useful load.

The two-dimensional convex model of the driverless transport vehicleloaded with the useful load can be created according to the followingprocess steps:

-   -   determining the outline of the plan view of the driverless        transport vehicle loaded with the at least one useful load and    -   forming a convex envelope of the outline in order to obtain the        two-dimensional convex model of the driverless transport vehicle        loaded with the useful load.

At least a part of the useful load and/or of the driverless transportvehicle as plan view can comprise at least one circular outline.Preferably before forming the convex envelope this circular outline isapproximated by its smallest enclosing square. This has advantages for arelatively efficient automated collision check.

For increased safety during the collision checking, preferably theconvex envelope can be inflated by a predefined safety distance in orderto obtain the two-dimensional convex model of the driverless transportvehicle loaded with the useful load.

Preferably the area covered is convex, i.e. comprises no indentations.The further area covered is preferably also convex. As a result, it canbe checked relatively efficiently, in particular using the separationtheorem whether the two convex areas covered overlap.

The planned movement of the driverless transport vehicle is, forexample, a turning of the driverless transport vehicle on the spot. Inthis case, the area covered is preferably executed as the smallestcircumscribed circle of the two-dimensional model. A circle is alsoconvex so that the area covered executed as a circumscribed circle isalso convex.

The planned movement of the driverless transport vehicle can run along aroute section. In this case, preferably for the area covered, theplanned orientations of the driverless transport vehicle are taken intoaccount at both ends of the route section.

The area covered can also be dependent on the type of planned movementalong the route section. Examples of the type of movement along theroute section are as follows: the driverless transport vehicle shouldmove along a virtual guide line. The driverless transport vehicle shouldmove autonomously along the route section.

The area covered by the driverless transport vehicle can, for example,be the circumscribed circle of the two-dimensional models at both endsof the route section. This area covered is convex and allows arelatively rapid and efficient collision check.

The area covered by the driverless transport vehicle can, for example,be the axially parallel enclosing rectangle of the two-dimensionalmodels at both ends of the route section. This area covered is alsoconvex. This area covered specifically models the movement of thedriverless transport vehicle more accurately than the circumscribedcircle but results in a somewhat higher computing expenditure for thecollision checking.

If, for example, the driverless transport vehicle should driveautonomously along the route section, the area covered can be thecombination of the occupied area of the two-dimensional models at bothends of the route section. This area covered is certainly not convex butits two components can preferably be executed as convex.

The area covered by the driverless transport vehicle can, for example,be a convex envelope which encloses the two-dimensional models at bothends of the route section. This modeling of the area covered isparticularly suitable when the orientations of the driverless transportvehicle at both ends of the route section should remain the same andwhen in particular, the driverless transport vehicle should move alongthe virtual guide line.

The area covered by the driverless transport vehicle can, for example,comprise the circumscribed circles of the two-dimensional models of thedriverless transport vehicle at both ends of the route section, whereinthe area covered is the convex envelope of these two circumscribedcircles. This model is particularly suitable when the orientations ofthe driverless transport vehicle at both ends of the route sectionshould differ and when in particular the driverless transport vehicleshould move along the virtual guide line.

According to one embodiment of the method according to the invention, itis provided that the collision checking is carried out by means of aplurality of hierarchical steps. In this case, in particular the areacovered in a following step is executed more accurately compared to itspreceding step but is more CPU-intensive for checking the overlap.Preferably the following step is only executed when, as a result of itspreceding step, the area covered by the driverless transport vehicleassigned to the preceding step overlaps the further area coveredassigned to the preceding step, should the further driverless transportvehicle also move, or overlaps the two-dimensional model of the furthertransport vehicle in the case where the further driverless transportvehicle is stationary.

Since the preceding step is executed computationally more efficiently,it can optionally be identified relatively rapidly that the plannedmovement in question can be executed free from collision.

For example, a first, a second, and a third hierarchical step can beprovided. In this case, it can preferably be provided that the areacovered of the first step is the circumscribed circle of thetwo-dimensional models at the two ends of the route section and the areacovered of the second step is the axially parallel enclosing rectangleof the two-dimensional models at both ends of the route section. Inparticular, the circumscribed circle as the area covered allows arelative computationally efficient checking of the overlap.

The third step preferably forms the last step. For this step inparticular the area covered is dependent on the type of plannedmovement. The area covered of the third step is, for example, thecombination of the occupied area of the two-dimensional models at bothends of the route section or the convex envelope, which encloses thetwo-dimensional models at both ends of the route section or comprisesthe circumscribed circles of the two-dimensional models of thedriverless transport vehicle at the two ends of the route section,wherein the area covered is the convex envelope of these twocircumscribed circles.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention are shown as an example in theappended schematic figures. In the figures:

FIG. 1 shows an environment and a graph assigned to the environment,

FIG. 2 shows a driverless transport vehicle,

FIGS. 3-7 show the modeling of a two-dimensional model of the driverlesstransport vehicle with transported useful load,

FIG. 8 shows a circumscribed circle as area covered by a driverlesstransport vehicle moving along a route section,

FIG. 9 shows an enclosing rectangle as area covered by a driverlesstransport vehicle moving along a route section,

FIG. 10 shows a circumscribed circle as area covered by a turningdriverless transport vehicle, and

FIGS. 11-13 show examples of areas covered by the driverless transportvehicle.

DETAILED DESCRIPTION

FIG. 1 shows an environment U and a graph G assigned to the environmentU. The graph G is, for example, stored in a central computer R andmodels the environment U. The computer R is in particular a so-calledfleet manager.

The graph G comprises nodes K and edges E connecting the nodes K. Theenvironment U comprises in particular points and route sections Sconnecting the intermediate points. The edges E are assigned to theroute sections S and the nodes K are assigned to the points.

A plurality of driverless transport vehicles should move within theenvironment U. One of the driverless transport vehicles 1 is shown inFIG. 2.

The driverless transport vehicle 1 shown schematically in FIG. 2 ispreferably configured in such a manner that it can move freely in alldirections. The driverless transport vehicle 1 is in particularconfigured as an omnidirectionally movable or holonomic driverlesstransport vehicle 1. The driverless transport vehicle 1 can be a mobilerobot, which comprises a robot arm having a plurality of successivelyarranged members, which are connected by means of articulations.

In the case of the present exemplary embodiment, the driverlesstransport vehicle 1 comprises a vehicle main body 2 and a plurality ofomnidirectional wheels 3, which are also designated as mecanum wheels.Such wheels comprise, for example a rotatably mounted rim, on which aplurality of rolling bodies are mounted in a driveless manner. The rimcan be driven by a drive. In the case of the present exemplaryembodiment, the wheels 3 are each driven by an electric drive 4. Theseare preferably regulated electric drives.

The driverless transport vehicle 1 further comprises an electroniccontrol device 5 arranged on the vehicle main body 2, which electroniccontrol device 5 is connected to the drives 4. Optionally these can alsoactivate the movement of the robot arm, if present.

The driverless transport vehicle 1 is provided to move automaticallywithin the environment U in particular from one of the points to afurther point and thus to pass at least one of the route sections S. Tothis end, a computer program runs on the electronic control device 5,which computer program activates the drives 4 in such a manner thatthese automatically move the driverless transport vehicle 1.

In the case of the present exemplary embodiment, that route along whichthe driverless transport vehicles should drive is planned by thecomputer R. To this end, a computer program runs on the computer R,which computer program initially plans paths within the graph G, whichare assigned to the corresponding route sections S, along which thedriverless transport vehicles should drive. In order that the individualdriverless transport vehicles receive the information relevant for themfrom the computer R, the computer R and the driverless transportvehicles or the electronic control devices thereof are adapted so thatthey can communicate with one another.

In the case of the present exemplary embodiment, it is provided thatwhen planning the paths, the computer R also takes into accountpotential collisions of two driverless transport vehicles 1 or plans thepaths in such a manner that collisions of two driverless transportvehicles 1 are avoided. To this end, in the case of the presentexemplary embodiment, the driverless transport vehicles 1 are modeled asareas which at least approximately model a plan view of the outlines ofthe individual driverless transport vehicles 1. The correspondingtwo-dimensional models or areas of the driverless transport vehicles 1are, for example stored in the computer R or are currently calculated.

In the case of the present exemplary embodiment, the driverlesstransport vehicles 1 are provided to transport at least one useful load.The useful load can, for example, project beyond the correspondingdriverless transport vehicle 1.

In the case of the present exemplary embodiment, when modeling thedriverless transport vehicles 1, the transported useful load thereof isalso taken into account.

FIGS. 3 to 7 illustrate an example as to how the driverless transportvehicle 1 with transported useful load can be modeled.

FIG. 3 shows a plan view of the driverless transport vehicle 1 or itsoutline. The outline corresponds in the case of the present exemplaryembodiment, substantially to a rectangle. Any information relating tothe outlines of the driverless transport vehicles 1 is, for example,stored in a database, which the computer R may access.

Furthermore, in the case of the present exemplary embodiment, theoutlines or any information relating to the outlines of possiblyprovided useful loads is also stored in the database. Thus, for example,FIG. 4 shows a plan view or the outlines of a circular useful load 6 andan angular useful load 7, with which the driverless transport vehicle 1is loaded and which each project beyond the driverless transport vehicle1.

In the case of the present exemplary embodiment, not the precise outlineof the driverless transport vehicle 1 loaded with the useful loads 6, 7is used for the modeling but, for example, for reasons of increasing theefficiency for a collision checking, all circular outlines areapproximated by the smallest square 8 enclosing them. This is shown inFIG. 5.

From the thus resulting outlines in the case of the present exemplaryembodiment, a so-called (two-dimensional) convex envelope 9 shown inFIG. 6 is formed. In mathematics or informatics, a convex envelope isunderstood as the smallest convex set, which contains the initial set. Asubset of a Euclidean space is then convex if for every two arbitrarypoints pertaining to the set, their connecting section also always liescompletely within the set. The convex envelope therefore comprises noindentations.

For an improved collision avoidance or collision check, the convexenvelope 9 modeling the loaded driverless transport vehicle 1, whichconvex envelope 9 is shown by the dashed line in FIG. 7 is subsequentlyextended or inflated by a safety distance or parametrizable distance,with the result that the two-dimensional convex model 10 of the loadeddriverless transport vehicle 1 shown in FIG. 7 is formed. Thetwo-dimensional convex model 10 is also convex, i.e. the two-dimensionalconvex model 10 is also a convex area or a convex polygon or a convexform. The two-dimensional convex model 10 therefore also has noindentations.

The reasons for the use of the convex envelope 9 or the two-dimensionalconvex model 10 instead of a form which models the loaded driverlesstransport vehicle 1 more accurately, which is usually not convex, caninter alia be the following: it could not be desirable that a so-calledfleet manager, i.e. the computer R, plans paths in which the loadeddriverless transport vehicles 1 move so that projecting components ofthe driverless transport vehicle or the useful loads 6, 7 move in freespaces, which are possibly obtained between other driverless transportvehicles 1 and their useful loads 6, 7. This risk is at least reduced,if not completely eliminated, by using the convex envelope 9 or thetwo-dimensional convex models 10. Secondly, as a result, the so-calledseparation theorem can be used for a collision check.

In the case of the present exemplary embodiment, a possible collision oftwo driverless transport vehicles 1 is checked during the planning ofthe path. In this case, the movement of at least one of the twodriverless transport vehicles 1 is taken into account or modeled bydetermining the area covered, which is at least occupied by the loadeddriverless transport vehicle 1 during a movement. The area covered isobtained, for example, if the driverless transport vehicle 1 turns onthe spot. The area covered is primarily that area covered by thedriverless transport vehicle 1 according to the planning of thecorresponding path along a determined route section S, to which twoadjacent nodes K and the appurtenant edge E of the graph G are assigned.

The area covered is in particular also convex, and therefore alsocomprises no indentations.

Finally it is checked whether this area covered overlaps a further areacovered, which is assigned to a further driverless transport vehicle 1.The further driverless transport vehicle 1 can in this case also move oreven stand still. If the two areas covered do not overlap, the loadeddriverless transport vehicle 1 can pass this route section S free fromcollision or turn on the spot and the corresponding route section S orthe corresponding turning can be used for planning the path. If thefurther driverless transport vehicle is stationary, its area coveredthen corresponds to its two-dimensional convex model.

For determining the area covered, in particular the potentially plannedorientations of the driverless transport vehicle 1 at both ends of theroute section S or the nodes K of the corresponding edge E are takeninto account.

For determining the area covered by the driverless transport vehicle 1,in the case of the present exemplary embodiment, the potential positionsand orientations of the driverless transport vehicle 1 are simulatedusing its two-dimensional convex model 10 at both ends of the routesection S in question by simulating the corresponding orientations atthe nodes K of the graph G, which are assigned to both ends of the routesection S in question. The area covered is obtained, for example, by acalculation of a convex envelope enclosing the two two-dimensionalconvex models 10.

In the case of the present exemplary embodiment, the checking of apotential collision is carried out via a plurality of steps, i.e. thereis a hierarchy of heuristics for the collision checking.

In the case of the present exemplary embodiment, in a first step theareas covered are approximated by relatively simple geometric forms. Forchecking a potential collision, checking routines between convexpolygons or convex forms and between convex polygons or forms andcircles are implemented on the computer R. In so doing, emphasis isplaced on the most efficient possible implementation. Theseimplementations are based in particular on the separation theorem. Theseparation theorem allows in many cases the absence of an intersection,i.e. of an overlap of convex geometric forms to be identified relativelyprematurely.

This relatively simple geometric form includes the entire area covered,which would be covered by the driverless transport vehicle 1 in questionduring passage through the route section S in question or when turningon the spot. In the first step, the area covered is selected relativelyinaccurately but relatively efficiently for an automated check.

In the case of the present exemplary embodiment, the collision checkusing a relatively accurate modeled area covered is preceded by twosteps or heuristics, which checks with relatively low expenditure and inmany cases can also already indicate the absence of intersections or acollision-free potential movement.

In the case of the present exemplary embodiment, initially in a firststep the circumscribed circles 11, see FIG. 8, of at least one of thedriverless transport vehicles 1 to be checked are determined as areascovered and checked for any overlap. Should an overlap be identified, ina second step, see FIG. 9, the respective axially parallel minimalenclosing rectangles 12 are checked for intersection. Both checks can beimplemented relatively efficiently and in the absence of an intersectionalready eliminate any intersection of the more precisely modeled areascovered.

If an overlap is obtained for the first step, the overlap of the secondstep is then checked. If an overlap is again obtained, then in a thirdand last step the overlap is checked based on the more accuratelymodeled form of the areas covered. If an overlap is again obtained, themovement in question cannot be implemented and is discarded for theplanning of the path in question.

In the first step, therefore in the case of the present exemplaryembodiment, the areas potentially covered by the driverless transportvehicles 1 are formed by means of the circumscribed circles 11. To thisend, for the driverless transport vehicles 1 in question and the routesections S in question or the assigned edges E, the orientations of thedriverless transport vehicle 1 are simulated using its convextwo-dimensional model 10 at both ends of the route section S in questionby simulating the corresponding orientations at the nodes K of the graphG, which are assigned to both ends of the route section S in question.

In FIG. 8 one of the convex two-dimensional models 10 of the driverlesstransport vehicle 1 is shown by dashed lines at one of the nodes K. Thesimulated movement of the driverless transport vehicle is such that itshould move from the node K, at which the two-dimensional convex model10 is shown by dashed lines, to the other node K, at which thetwo-dimensional convex model 10 is shown by continuous lines. Thecircumscribed circle 11 as the area covered of the first step enclosesthe two two-dimensional convex models 10 at both nodes K.

FIG. 10 shows an example of a driverless transport vehicle 1 turning onthe spot with corresponding smallest circumscribed circle 13 as areacovered.

In the second step in the case of the present exemplary embodiment, theareas potentially covered by the driverless transport vehicles 1 areformed by means of the enclosing axially parallel rectangle 12. To thisend, for the driverless transport vehicle 1 and the route section S inquestion of the assigned edge E, the orientations of the driverlesstransport vehicle 1 are simulated using its two-dimensional convex model10 at both ends of the route section S in question by simulating thecorresponding orientations at the nodes K of the graph G, which areassigned to both ends of the route section S in question. In FIG. 9 oneof the two-dimensional convex models 10 of the driverless transportvehicle 1 is shown by dashed lines at one of the nodes K. The simulatedmovement of the driverless transport vehicle 1 is such that it shouldmove from the node K, at which the two-dimensional convex model 10 isshown by dashed lines, to the other node K at which the convextwo-dimensional model 10 is shown by continuous lines. The enclosingaxially parallel rectangle 12 as the area covered of the second stepencloses the two two-dimensional convex models 10 at both nodes K.

In the case of the present exemplary embodiment, the form of the areacovered in particular of the third step can also depend on the type of apotential movement. Thus, for example, it can be provided that thedriverless transport vehicle 1 should travel along a determined routesection S along a virtual guide line. However, it can also be providedthat the driverless transport vehicle 1 should autonomously travel adetermined route section S, e.g. by evaluating images of the environmentU.

FIGS. 11 to 13 show a few examples of areas covered for the third step.

FIG. 11 shows an area covered 14 during a potential autonomous movementof the driverless transport vehicle 1 along a determined route sectionS. In this case, only the occupied area at the beginning of the movementand the occupied area at the end of the movement along the route sectionS in question are used as area covered 14, i.e. the area covered 14 isthe combination of the two-dimensional convex models 10 at the nodes K,which are assigned to the route section S in question. In this casetherefore, only the planning form, i.e. the two-dimensional convex model10 of the driverless transport vehicle 1 is taken into account at thetwo nodes K. In particular, the collision checking is carried outseparately for the two two-dimensional convex models at both ends of theroute section in question.

FIG. 12 shows an example of a simulated movement of the driverlesstransport vehicle 1, e.g., along a virtual guide line. The orientationsof the driverless transport vehicle 1 are the same at both ends of theroute section S in question or at both nodes in question. The driverlesstransport vehicle 1 should therefore not change its orientation duringthe movement. In this case, the area covered is a further convexenvelope 15, which encloses the two-dimensional convex models 10 at bothnodes K, which are assigned to the route section S in question.

FIG. 13 shows an example of a simulated movement of the driverlesstransport vehicle 1, e.g., along a virtual guide line. The orientationsof the driverless transport vehicle 1 are different at both ends of theroute section S in question or at the two nodes in question. Thedriverless transport vehicle 1 should therefore change its orientationduring the movement. In this case, e.g. for determining the areacovered, firstly the circumscribed circles 16 of the two-dimensionalconvex models 10 are determined at the two nodes K in question and thena convex envelope 17 is determined as area covered, which convexenvelope 17 encloses the circumscribed circles 16 at the two nodes K,which are assigned to the route section S in question. In particular,the convex envelope 17 encloses the two circumscribed circles 16 and arectangle 18 with four sides. In each case, two of the sides areopposite so that the rectangle 18 has two pairs of sides, which eachcomprise two of the opposite sides. The lengths of the sides of one pairof sides correspond to the lengths of the edge E in question and thelengths of the sides of the other pair of sides correspond to thediameters of the circumscribed circles 16 in question. The sides of oneof the pairs of sides run through the node K.

The collision checking can be carried out in particular by using the twocircumscribed circles 16 individually, and separately the rectangle 18instead of the complete convex envelope 17.

In this way, it can be ensured in particular that the differentproperties of different types of movements are suitably taken intoaccount.

The form used to calculate the area covered in question is in particulardependent on the orientation at the beginning of the movement along anedge E and a planned orientation at the end of the movement. If bothorientations agree, preferably for the third step, precisely the areawhich is covered by the planning form, i.e. the two-dimensional convexmodel 10, in the case of the present exemplary embodiment, of the loadeddriverless transport vehicle 1 while maintaining this orientation istaken into account. This results in a convex polygon, i.e. the convexenvelope 15, which is essential for the use of the preferably usedseparation theorem.

Otherwise, for example, account is taken of the area covered, which iscovered by the circumscribed circle 16 of the planning form of thedriverless transport vehicle 1 when this circumscribed circle 16 ismoved from one of the nodes K to the other node K of the correspondingedge E. This in turn yields a convex form, i.e. the convex envelope 17.

Furthermore, at least the risk that two driverless transport vehicles 1traveling past one another turn past too close to one another can be atleast reduced by preferably taking into account exclusively convexforms.

One of the driverless transport vehicles can also be stationary for thecollision checking or turn on the spot.

In this way, both the movement along the edge E or the correspondingroute section S can be taken into account as well as the plannedorientation.

1. A method for checking a collision between a driverless transportvehicle (1) and a further driverless transport vehicle during a planningof a movement of at least the driverless transport vehicle (1)comprising the following process steps: providing two-dimensional modelsof the driverless transport vehicles (1), determining an area covered bythe driverless transport vehicle (1) which the driverless transportvehicle (1) covers during the planned movement and determining a furtherarea covered by the further driverless transport vehicle, which iscovered by the further driverless transport vehicle during the plannedmovement and checking a collision between the driverless transportvehicle (1) and the further driverless transport vehicle by checking thetwo areas covered for any overlap or checking a collision between thedriverless transport vehicle (1) and the further driverless transportvehicle by checking the area covered assigned to the driverlesstransport vehicle (1) for any overlap with the two-dimensional model ofthe further transport vehicle.
 2. The method as claimed in claim 1,comprising: discarding the planning or the part of the planning inquestion when the two-dimensional model of the further driverlesstransport vehicle overlaps with the area covered or discarding theplanning or the part of the planning in question when the two areascovered overlap.
 3. The method as claimed in claim 1, in which thedriverless transport vehicles (1) are each loaded with at least oneuseful load (6, 7) and the two-dimensional models are two-dimensionalconvex models of the driverless transport vehicles (1) loaded with theuseful loads (6, 7).
 4. The method as claimed in claim 3, in which thetwo-dimensional convex model of the driverless transport vehicle (1)loaded with the useful load (6, 7) is created according to the followingprocess steps: determining the outline of the plan view of thedriverless transport vehicle (1) loaded with the at least one usefulload (6, 7) and forming a convex envelope (9) of the outline in order toobtain the two-dimensional convex model of the driverless transportvehicle (1) loaded with the useful load (6, 7).
 5. The method as claimedin claim 4 in which at least a part of the useful load (6) and/or of thedriverless transport vehicle (1) as plan view comprises at least onecircular outline and before forming the convex envelope (9) the circularoutline is approximated by its smallest enclosing square (8).
 6. Themethod as claimed in claim 4 comprising: inflating the convex envelope(9) by a predefined safety distance in order to obtain thetwo-dimensional convex model (10) of the driverless transport vehicle(1).
 7. The method as claimed in claim 1, in which the area covered isconvex.
 8. The method as claimed in claim 1, in which the plannedmovement of the driverless transport vehicle (1) is a turning of thedriverless transport vehicle (1) on the spot and the area covered is thesmallest circumscribed circle (13) of the two-dimensional model.
 9. Themethod as claimed in claim 1, in which the planned movement of thedriverless transport vehicle (1) runs along a route section (S).
 10. Themethod as claimed in claim 9, in which for the area covered the plannedorientations of the driverless transport vehicle (1) are taken intoaccount at both ends of the route section (S) and/or in which the areacovered is dependent on the type of planned movement.
 11. The method asclaimed in claim 9, in which the area covered by the driverlesstransport vehicle (1) is the circumscribed circle (11) of thetwo-dimensional models at both ends of the route section (S) or is theaxially parallel enclosing rectangle (12) of the two-dimensional modelsat both ends of the route section (S) or is the sum of the occupied areaof the two-dimensional models at both ends of the route section (S) oris a convex envelope (15) which encloses the two-dimensional models atboth ends of the route section (S) or comprises the circumscribedcircles (16) of the two-dimensional models of the driverless transportvehicle (1) at both ends of the route section (S) and the area coveredis the convex envelope (17) of these two circumscribed circles (16). 12.The method as claimed in claim 1, in which the checking of the collisionis carried out by means of a plurality of hierarchical steps, whereinthe area covered in a following step is executed more accuratelycompared to its preceding step but is more CPU-intensive for checkingthe overlap and the following step is only executed when, as a result ofits preceding step, the area covered by the driverless transport vehicle(1) assigned to the preceding step overlaps the further area coveredassigned to the preceding step or overlaps the two-dimensional model ofthe further transport vehicle.
 13. The method as claimed in claim 12,comprising a first, a second and a third hierarchical step, wherein inparticular the area covered of the first step is the circumscribedcircle (11) of the two-dimensional models at the two ends of the routesection (S) and the area covered of the second step is the axiallyparallel enclosing rectangle (12) of the two-dimensional models at bothends of the route section (S).
 14. A system, comprising a driverlesstransport vehicle (1), a further driverless transport vehicle (R) and acomputer which is able to communicate with the driverless transportvehicles, wherein the computer (R) is adapted to carry out the method asclaimed in claim 1.